This application is entitled to the benefit of Australian Documents Complete Specification 75596/01 filed Sep. 24, 2001 associated with Provisional Document PR 3389 filed Feb. 28, 2001.
This invention relates to a small low cost machine vibration tester with hand-held operation for vibration testing and data recording by typically factory maintenance workers repairing or operating low cost and non-critical machinery which has a speed of rotation speed of typically less than 12,000 revolutions per minute.
Much of the current machine vibration testing equipment is expensive, sophisticated, to scientific instrument standard, and are not commonly used by the majority of maintenance workers, except on expensive machinery. Maintenance workers who repair and often operate machines are often permanently working on site and often have the best time saving cost advantage to use machine vibration testing devices. Machine vibration testers assist in fault finding and repair work on machines.
The art of machine vibration monitoring in the 1930""s was a variable length reed vibrometer which was a simple reed type spring, weight, holder, device. This device only has a few dollars of parts. For the vibrometer the amplitude of vibration of the spring when at resonance is an indication of machine vibration at the set frequency, hence acting as a distorted accelerometer with air damping of the moving spring, producing a variation in damping factor at different frequencies. The amplitude of the spring vibration is a measure of vibration but not necessarily in engineering units. While I believe air damping in the previous causes the distortion of amplitude at different frequencies, I don""t wish to be bound by this.
This vibration tester is an update of the vibrometer using modern technology and the minimum of common electronic components.
Most current machine vibration monitoring devices use expensive calibrated transducers that converts the mechanical vibration into a voltage signal proportional to the mechanical vibration in engineering units of vibration (for example possibility mm/s RMS-velocity transducer, g-acceleration transducer, etc.). The calibrated transducer electrical signal output is then conditioned and analysed by very sophisticated and complex computer type circuits, especially for fast fourier transform (FFT) analysis, and then displayed in engineering units of vibration usually on a computer type screen. These expensive vibration transducers are mounted by various means such as epoxy, cyanoacrylate cement, threaded stud, permanent magnet, and are less commonly hand-held. Mounting the vibration transducer greatly increases the likelihood of exact repeatable results and reduces the risk of gross errors. The operating conditions of the machine subject to vibration testing can greatly effect vibration levels indicated. This applies especially to machines that can run at different load conditions.
The vibration tester in the prototype embodiment or basic embodiment relates to a hand-held machine vibration tester and writing instrument comprising a small match box sized housing for an electronics circuit mounted on a liquid marking line writing pen body, so that the pen body can be held urging the housing mounted vibration probe against a machine surface to test machine vibration.
The housing exposes an electronic display indicating levels of vibration amplitude to four predetermined levels each designated by the illumination of a different coloured light emitting diode.
The vibration test result can be written on the machine surface as a permanent record of the vibration test and the exact test position on the machine surface.
The vibration tester has electrical connection to facilitate more detailed vibration tests using electrical connection to multimeter, computer, and other electrical equipment.
Several objects and advantages of my vibration tester are:
Simple operation and design for on going use day after day on the factory floor. The only simpler device is the variable length vibrometer which is more time consuming to adjust and take amplitude readings. The vibrating reed is especially hard to observe in dark machinery spaces. In contrast the illumination of the LED""s to indicate level of vibration amplitude facilitates use in dark machinery spaces.
Maintenance workers traditionally disassemble machines to find the cause of observed excess machine vibration. This often easily finds the cause for machine vibration problems including, loose rotating shafts in bearings, damaged rolling element bearings, bent shafts, loose components on rotating assemblies, plus others.
Sometimes visual inspection of disassembled parts will not verify
imbalance of rotating assemblies,
electrical faults in electrical alternating current motors,
some V-belt drive problems,
plus others as the cause of the excess vibration.
The vibration tester connected with a digital multimeter as described later can verify some of the listed causes of excess vibration that are not obvious from a visual inspection of disassembled parts.
The vibration tester is hand-held when taking vibration readings which is convenient for a quick look survey. Hand-held vibration readings can have errors and poor likelihood of exact repeatable results. The vibration tester is only intended to indicate significant increases in vibration from the previous vibration reading. This reduces the risk of false alarm type repairs.
Importantly the permanently written data on the machine surface also acts as a long term memory aid to maintenance workers. As even small factories can have hundreds of machines. Every maintenance worker at some time has stood looking at troublesome machine wondering if the machine is vibrating more than when it was brand new and reliable.
Excess machine vibration in some machines can cause repeated breakdowns and unreliability. If the cause of vibration is diagnosed and repaired a previous troublesome machine can become reliable again. In some machines a red LED illumination vibration level would indicate excess machine vibration.
The vibration tester if mass produced would be priced in the range of an engineering consumable product and could be replaced if broken. The current state of art xe2x80x9cengineering unit(s)xe2x80x9d calibrated transducers currently are too expensive to be considered a consumable product.
This vibration tester consists of the minimum hardware to give the operator a minimal visual indication of a possible significant change in machine vibration from a previously recorded vibration datum.
On the occasions, when more information is required, the vibration tester, has the potential to provide this. If the vibration tester is mass produced to a suitable level of conformity, suitable software would digitally correct the output signal to engineering units of vibrations. The software could perform a digital correction and fast fourier transform analysis in engineering units of vibration. This provides the option to use the vibration tester connected to a laptop computer, when more information is required to determine the reason for an increase in machine vibration within standard engineering vibration parameters perhaps using machinery manufacturers vibration data.
It is envisaged that the vibration tester singularly would be used for day to day testing in a typical factory. The vibration tester and laptop computer would only be used on odd occasions perhaps every couple of months. The laptop computer is less likely to be damaged from a rough factory environment with this pattern of use.